Question

4. Calculate
a. q when a system does 54J of work and its energy decreases by 72 J
b. ∆E for a gas that releases 38J of heat and has 102J of work done on it.

Answer 1

a) The first law of thermodynamics helps us in calculating the amount of heat absorbed or released.

From the formula;$\Delta_E$ $=q+w$

$q=\Delta_E$ $-w$

$\therefore$ $q=(-72J)-(-54J)$

$=-18J$

b) Using the first law of thermodynamics helps us to calculate the change in internal energy. $q$ in this case is a negative value since the system releases energy.

$\Delta_E=q+w$

$=(-38J)+(+102J)=+64J$